Method of making daily cover for a landfill

ABSTRACT

A method of recycling construction and demolition debris to produce an article suitable as a daily cover for a landfill is disclosed. The method generally comprises the steps of removing large pieces of metal from the debris, compacting the balance of the debris into small pieces, shredding the debris into smaller particles, separating the ferrous and optionally the non-ferrous metals from the debris utilizing the combination of magnetic, air and/or water separating systems, dewatering the shredded debris to produce a product suitable for use as a daily cover for a landfill.

FIELD OF THE INVENTION

The present invention relates to a method of recycling construction anddemolition debris and an article produced by the method. Moreparticularly, the invention relates to a method of recyclingconstruction and demolition debris into an article useful as a daily orperiodic cover for a landfill.

BACKGROUND OF THE INVENTION

Federal and state environmental regulations require the operators ofsanitary landfill operations to periodically cover disposed solid wastewith six inches of earthen material to control disease, insects, fires,odors, blowing litter, and scavenging. For example, most jurisdictionsrequire such covering of sanitary landfills at the end of each operatingday, or at more frequent intervals if necessary. This coveringrequirement and the cover material is known as "daily cover" or"periodic cover" where the regulatory interval is more than one day,e.g., three days. As used herein, "daily cover" is intended to includedaily and periodic cover for sanitary landfills, such as municipal solidwaste (MSW) landfills, rubble landfills and land clearing debrislandfills, and industrial waste landfills.

Each day's garbage, trash or rubble layer is covered at the end of theday and further garbage, trash or rubble layers are then spread directlyon top of the daily cover for the previous day. In many landfill sitesthe soil used for the daily cover must be mined at the landfill site orpurchased from an outside source and, due to the high rate of soilconsumption, comprises a substantial cost item. Moreover, it has beenrecognized that multiple earth fill layers used in this way consume asignificant volume of the valuable landfill space which might otherwisebe used for receiving garbage, trash or rubble. It is well known thatmany communities are rapidly exhausting their available landfill acreageand it is therefore desirable to reduce the consumption rate of theavailable landfill volume. Accordingly, federal and state regulationsallow alternative, more compressible, daily cover materials in lieu ofthe six inches of earthen material so long as the alternative materialsprovide the requisite level of protection.

Several such alternative daily cover materials are known in the art. Onealternative, disclosed in U.S. Pat. No. 4,519,338 to Kramer et al,comprises hardenable plastic foam cover which is applied to the wastematerial by spraying. Similarly, companies such as 3M EnvironmentalProtection Products of St. Paul, Minn., Chubb Environmental Security ofExton, Pa., and Russmer of Westchester, Pa., have all developedsynthetic foams which can be sprayed onto a landfill face each day tofunction as a daily cover.

One disadvantage of such foam spray daily covers is that the highpressure spray equipment utilized to apply the foam tends to blow awaythe waste material to which it is applied. Additionally, the foam spraysolution is expensive, typically 12 to 15 cents per square foot,substantially more expensive than dirt. Furthermore, weatherrestrictions, such as heavy rain or extreme cold and wind, hampers boththe installation and performance of foam covers.

Another disadvantage of the foam daily cover substitutes is that itcannot be easily formulated from recycled materials. The increasingsensitivity towards the environment by society at-large has greatlyincreased the demand for using recycled products. State and municipalenvironmental officials, who operate or regulate most landfills, havebeen especially active in encouraging use of recycled products. Amongthe advantages of recycling is the fact that the waste material isconverted into useful products rather than taking up rapidly depletinglandfill space. Hence, such officials are making great efforts tointegrate recycled materials into operations under control of theirgovernments, including landfill operations.

Another alternative to using earthen material as a daily cover isdisclosed in U.S. Pat. Nos. 4,909,667 to DeMello and 4,927,317 toAcosta. DeMello and Acosta disclose a geotextile or sheet-like member,such as canvas and the like, which is laid over the working face of alandfill at the end of the operating day. Similar geotextile dailycovers include the Fabrisoil® non-woven polypropylene geotextilemanufactured by the Phillips Fiber Corp. of Greenville, S.C. as well asthe Sani-Cover™ polypropylene geotextile manufactured by Amoco FibersCorp. of Atlanta, Ga. A key disadvantage of geotextile covers is theirexpense which may be as high as $2.25 per square yard. In addition,geotextiles are subject to mechanical damage, such as tears, puncturesand the like, require replacement or repair and are difficult to applyin inclement weather.

SUMMARY AND OBJECTS OF THE INVENTION

In view of the foregoing limitations and shortcomings of the prior artmethods and daily cover materials, as well as other disadvantages notspecifically mentioned above, it should be apparent that there stillexists a need in the art for an alternative to conventional earthenmaterial daily cover which is inexpensive, space saving, and made fromrecycled materials.

More particularly, it is an object of this invention to provide a dailycover alternative which is substantially more compressible than dirt.

It is another object of this invention to provide a daily coveralternative which is made entirely from recycled materials, inparticular, construction and demolition debris.

Yet another object of this invention is to provide a method of disposingof construction and demolition debris in a manner that is economical,environmentally sound, and practical.

The aforementioned objects are accomplished according to the inventionby a method of converting construction and demolition debris into dailycover for a landfill. "Construction and demolition debris," as usedherein and as typically defined by state and municipal laws andordinances, comprises debris associated with the razing of buildings,roads, bridges, and other structures and/or debris associated with theconstruction of buildings. It typically includes, but is not limited to,ferrous and non-ferrous metals, concrete, bricks, lumber, plaster andplasterboard, insulation material, cement, shingles and roofingmaterial, floor, wall and ceiling tile, asphalt, glass, pipes and wires,carpet, wallpaper, felt and other items physically attached to thestructure, including compacted appliances, structural fabrics, paper orcardboard packaging. Typically excluded from construction and demolitiondebris are materials that pose an undue risk to public health or theenvironment such as industrial waste or byproducts, paint, tar,solvents, creosite, adhesives and the like.

It is not intended that the above listing of specific debris items beall-inclusive of the items of debris which may be incidentally presentin construction and demolition debris. It is within the contemplationand scope of the present invention that limited or incidental amounts ofother debris items may be present in construction and demolition debriswithout altering either its essential characteristics as constructionand demolition debris or its suitability for recycling into daily coveraccording to the method of the invention. Such other debris items mayinclude, e.g., tires, brush and limbs, rock, etc.

In some cases, construction and demolition debris must be deposited inwhat are commonly known as "rubble" landfills which are required tosatisfy stringent design and operational requirements. However,according to the method of the present invention, the construction anddemolition debris is converted into a useful byproduct which can be usedas a daily cover for a sanitary landfill rather than being disposed ofas the contents of the landfill. This daily cover can be used not onlyfor municipal solid waste, land clearing debris and rubble landfills,but also for industrial waste landfills which are subject to evenstricter regulation. Briefly described, the method of the inventioncomprises the steps of removing large pieces of metal from the debris,compacting the balance of the debris into small pieces, shredding thepieces into even smaller particles, separating the ferrous andoptionally the non-ferrous metals from the debris utilizing acombination of magnetic, air and/or water separating systems, anddewatering the shredded debris to produce a daily cover suitable for useas a daily cover for a landfill.

The daily cover product of the present invention also advantageouslyfunctions as a more effective filter medium than the conventionalearthen daily cover materials thereby resulting in a cleaner leachatearriving at the bottom of a landfill using the daily cover of theinvention. The product of the method of the invention may thus be usedin a landfill as daily cover and as a filter medium. Alternatively, theproduct may be used as a filter medium to filter a liquid stream inapplications other than landfills as well as a filter medium for liquidstreams in landfill operations.

A further advantage of the present invention resides in the fact thatconstruction and demolition debris includes items, such as cement,concrete, plaster board and the like, containing calcium oxide or lime.The presence of lime in a daily cover layer thus advantageously reducesthe acidity level of the leachate reaching the bottom of the landfillsite.

With the foregoing and other objects, advantages and features of theinvention that will become hereinafter apparent, the nature of theinvention may be more clearly understood by reference to the followingdetailed description of the invention, the appended claims and to theattached drawing.

BRIEF DESCRIPTION OF THE DRAWING

The drawing is a flow diagram in block form showing the presentinvention in the stages which can be used in the course of recycling theconstruction and demolition debris into daily cover.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawing wherein there is illustrated a flow diagramin block form showing the preferred stages utilized in the course ofrecycling construction and demolition debris according to the presentinvention.

The process begins with the transport of construction and demolitiondebris to a processing center as shown in block 10 of the drawing. Afterthe construction and demolition debris arrives at the processing center,large pieces of metal are removed from the debris by a crane and placedin a collection area as shown in blocks 12 and 14 of the drawing.

The balance of the material is then moved to a "compacting" area whereit is compacted as seen in block 16 of the drawing. Compacting is theprocess of reducing the size of the material ("presizing") to allow itto be more efficiently fed to and processed by a shredder. A wheelcompactor machine is typically used for compacting. One suitable machinethat has been found effective in this compacting or presizing process isthe Ingersoll Rand 750 Wheel Landfill Compactor. This compactor hasspiked wheels which grind and cut the debris into smaller pieces in theprocess of compacting it. Other types of compacting machines may also beused.

After compacting, the material is fed into a shredding apparatus asshown in block 18 where it is reduced to even smaller pieces having anaverage particle size of six inches or less and preferably an averageparticle size of three inches or less. As used herein, "average particlesize" means the average sizes of all particles where the particle sizeis determined by the average of the particle dimensions. Thus, anindividual particle may have a dimension well in excess of six inches solong as the average dimensions of that particle and all other particlesaverage less than six inches, or preferably three inches.

The compacted debris is loaded onto a steel belt conveyor whichtransports the material into the inlet of the shredder. One shredderwhich has been found to be especially suitable for purposes of theinvention is an automotive shredder known as the Newell Super Heavy DutyShredder Model No. 80104TBD manufactured by Newell Industries, Inc. ofSan Antonio, Tex. The Newell shredder has a rotor diameter of 80" and awidth of 104" and is powered by a 3000 hp electric motor. The Newellmachine is a "wet shredder" because water is added directly into theshredding chamber which houses the rotor in order to prevent theemission of large clouds of dust that would otherwise be generatedduring the shredding process. Other shredders and crushers, includingwet and dry shredders and crushers, may also be used so long as therequired average particle size is attained. Super heavy duty shreddersof the general type described above are particularly preferred becauseof their ruggedness and capacity to receive unshreddables without damageand to reduce the debris to an appropriate particle size.

To more efficiently reduce the construction and demolition debris to theappropriate particle size, ferrous metal items may be optionally addedas a separate input stream to the shredder. Such additional ferrousmetal items function in the shredder in a manner similar to the balls ina ball mill to enhance the shredding process.

After shredding, the shredded material preferably undergoes a magneticseparation process as shown in blocks 20 and 22 to remove ferrous metalwhich can be of commercial value. The magnetic separator is preferably adrum type electromagnetic separator of conventional design. Afterferrous metals are removed, the shredded debris optionally undergoes anair or water separation process as shown in blocks 24 and 26 to recovervaluable non-ferrous metals such as copper, aluminum, etc.

If a wet shredder is used, the shredded, non-metallic debris is thendewatered as shown in block 28 to remove excess water so that theresulting product has an acceptable moisture content. If a dry shredderis used, water is added to moisten the material to a desired moisturecontent so as to give it sufficient weight and consistency for use asdaily cover. The moisture content may be in the range of about 5% toabout 30% by weight, is preferably in the range of about 10% to 14% byweight and most preferably about 12% by weight. Excess water from thedewatering step is preferably reused in the shredding step 18 if a wetshredder is employed or piped to the water separation step 24 if a dryshredder is used. If a dry shredder is used in the shredding step 18 andthe water separation step 24 is omitted, water 30 is added to theshredded debris to raise its moisture content to a level above thedesired range before passing it to the dewatering step 28 to adjust themoisture content to the desired range. Dewatering is preferablyaccomplished in a dewatering press, but may be accomplished by othermeans or by natural drainage. A water source 32 is provided forsupplying additional water to the excess water 30 or for directlysupplying the wet shredder 18 and/or the water separator 24. Water flowis represented by dashed lines in the drawing.

The output of the dewatering step 28 is daily cover product 34 in theform of moist recycled construction and demolition debris. The articleproduced according to the method of the present invention is suitable asan alternative daily cover for all types of landfills including,municipal solid waste, land clearing debris, rubble, and industrialwaste landfills.

Although certain presently preferred embodiments of the invention havebeen described herein, it will be apparent to those skilled in the artto which the invention pertains that variations and modifications of thedescribed embodiment may be made without departing from the spirit andscope of the invention. Accordingly, it is intended that the inventionbe limited only to the extent required by the appended claims and theapplicable rules of law.

What is claimed is:
 1. A method of making daily cover for a landfillcomprising the steps of:providing a supply of construction anddemolition debris; adding water to said debris; and processing saiddebris through a shredder so as to produce a moist shredded producthaving an average particle size and a moisture content sufficient topermit use of said product as daily cover for a landfill.
 2. The methodof claim 1, including the step of applying said product to a landfill asdaily cover.
 3. The method of claim 1, wherein said average particlesize is less than about six inches and said moisture content is about 5%to 30% by weight.
 4. The method of claim 1, wherein said averageparticle size is less than about three inches and said moisture contentis about 10% to 14% by weight.
 5. A method of disposing of wastematerial in a landfill wherein construction and demolition debrisprocessed in accordance with claim 1 is used as daily cover for alandfill.
 6. The method of claim 1, including the step of compactingsaid debris prior to processing said debris through said shredder. 7.The method of claim 1, including the step of separating ferrous metalfrom said debris after processing said debris through said shredder. 8.The method of claim 1, including the step of separating non-ferrousmetal from said debris after processing said debris through saidshredder.
 9. The method of claim 1, including the step of adding ferrousmetal items to said debris prior to processing said debris through saidshredder.
 10. The method of claim 1, wherein the water is added afterprocessing said debris through said shredder.
 11. A method of disposingof waste material in a landfill comprising the steps of:dumping a firstlayer of waste material on a landfill site; applying a first daily coverlayer of wet shredded construction and demolition debris processed inaccordance with claim 1 over said first layer of waste material; dumpinga second layer of waste material over said first daily cover layer; andapplying a second daily cover layer of wet shredded construction anddemolition debris processed in accordance with claim 1 over said secondlayer of waste material.
 12. The method of claim 11, including thefurther steps of dumping additional layers of waste material on saidsite and applying an additional daily cover layer of wet shreddedconstruction and demolition debris processed in accordance with claim 1over each of said addition layers of waste material.
 13. The method ofclaim 12, wherein said waste material is at least one of municipal solidwaste, land clearing debris, rubble and industrial waste.